This invention relates to a machine housing with a structural member which at least partially encloses a space containing at least a small quantity of liquid, which has relatively thin walls, and in which vibrations are produced by mechanical, pneumatic and/or hydraulic means.
The structural members with which the present invention is concerned are members of such types as are used, e.g. in internal combustion engines, for example as cylinder head covers, gear box covers, oil pans and the like. In these members, vibrations are produced (mechanically, pneumatically and/or hydraulically, through moving machine parts), with accompanying production of loud noise. A wide diversity of measures have heretofore been employed in attempting to attenuate these noises.
One such known expedient is to construct the structural member with relatively thick walls or with individual reinforcement of the wall or walls. This requires use of increased quantities of material in the structural members, which is not only expensive but also increases the weight of the machine housing, contrary to the present-day preference for lightweight construction.
Another known expedient is to coat the structural member with insulating material, e.g. rubberlike flexible layers, to attenuate the noise. These insulating materials, however, are not only expensive but also tend to come loose over the course of time, whereupon their effectiveness in attenuating the noise is reduced.